We have defined a new gene family, the Passover family, whose members apparently code for the invertebrate gap junction channel. Thirty members sharing high sequence homology are known. Mutants are available for five members: mutations in three family members are viable and alter a few specific gap junctional connections; two genes are expressed widely and are mutable to lethality. The founding member of the family, Passover (Pas), has been expressed in Xenopus oocytes where it forms intercellular channels. This proposal seeks to start defining the properties of the junctions made by pas family genes. The genes will be expressed in specific cells in Drosophila by using the GALA-UAS system and in heterologous systems such as Xenopus oocytes and tissue culture cells by injection of RNA and by transfection. We will determine how different the channels made by different genes are and whether the different channel molecules form homotypic or heterotypic channels. In the animals, PAS is expressed in the neurons of the Giant Fiber system (GFS) which are connected by gap junctions. Pas mutations disconnect these cells. We will determine whether different transcripts rescue different synapses. Chimeric channel genes have been made and will be used to determine whether various aspects of function can be mapped to different molecular domains. A genetic screen will be undertaken to find molecules that interact with pas. Health significance: The pas family proteins have no known homologs in vertebrates. Drugs that target them specifically should be safe for human and vertebrate animals. This could lead to drugs that kill nematodes and other parasitic worms of plants and animals, These drugs should also be effective against insects, like the malaria mosquito, the tsetse fly, the deer tick, etc. for humans, as well as a host of ectoparasitic insects ( and probably mites) of veterinary importance. Of course, a prime target would be insects and other invertebrates that infest and east food crops. Identification of the molecules which form invertebrate gap junctions allows the methods of experimental crops. Identification of the molecules which form invertebrate gap junctions allows the methods of experimental manipulation available in flies and worms to be immediately useable for studies of gap junction communication. This should greatly facilitate studies of developmental mechanisms, channel function and neural systems.